Groundwater and its response to climate variability and change in cold snow dominated regions in Finland: methods and estimations

• Main Author: Okkonen, J. (Jarkko)
• Other Authors: Kløve, B. (Bjørn)
• Format: Doctoral or Postdoctoral Thesis
• Language: English
• Published: Oulun yliopisto 2011
• Subjects: cold climate; conceptual framework; esker aquifer; geochemistry; numerical model; statistical model; geokemia; harju akviferi; konseptuaalinen viitekehysmalli; kylmä ilmasto; numeerinen malli; tilastollinen malli; Harju; Northern Finland
• Online Access: http://urn.fi/urn:isbn:9789514297014

Abstract A conceptual framework was developed to assess how changes in temperature and precipitation affect sub-surface hydrology, groundwater recharge, groundwater quantity and quality. A conceptual and statistical approach was developed to predict groundwater level variations. Daily rainfall, snowmelt and evapotranspiration values were generated with a novel conceptual hydrological model developed in this study. These values were cross-correlated with observed groundwater levels to find representative time lags and significant correlations. A statistical model linking rainfall, snowmelt, evapotranspiration and groundwater level was then developed and validated. The model simulated seasonal variations in groundwater level very accurately. A sequential approach was developed to assess surface water-groundwater interactions. The simulated surface water level estimated with the WSFS model and recharge estimated with CoupModel were linked to the groundwater flow model MODFLOW. Groundwater, surface water and snow samples were collected to study the chemical composition of groundwater in an unconfined esker aquifer in Northern Finland. Concentrations of Ca2+, Cl-, NO3-N and SiO2 and electrical conductivity were determined. Water quality in the main aquifer was found to be similar to that in the perched groundwater. Solute concentrations generally decreased during and immediately after snowmelt periods, indicating the importance of snowmelt input for groundwater quality. In the perched groundwater, NO3-N concentration increased with elevated groundwater level, indicating a nitrogen source on the land surface. The Cl- concentration in groundwater decreased when the surface water level rose higher than groundwater level. According to simulation results for the A1B climate change scenario, groundwater recharge is projected to increase in winter months due to increased snowmelt and decreased soil frost depth. The spring snowmelt peak in late spring will decrease. This will reduce aquifer storage in early spring, ...